1. Field of the Invention
This invention relates to antennas for wireless communications; and more particularly, to a novel antenna structure herein termed a “Vivaldi-Monopole Antenna” that is configured for ultra-wideband operation.
2. Description of the Related Art
Those having skill in the art will appreciate the difficulty in forming an antenna that exhibits stable radiation performance across the ultra-wide bandwidth, especially where low frequency communications bands are desired.
For this reason, there is a continued need for ultra-wideband antennas having relatively small form factor for integration with a variety of portable wireless devices.
In the prior art, an antenna structure known as a “Vivaldi Antenna” is described as having a tapered notch configured to achieve ultra-wide band resonances. Vivaldi antennas are generally understood by those in the art; however, further review of such antennas can be accomplished with an internet search. Accordingly, a detailed review of Vivaldi antennas is not provided herein.
In the Vivaldi antenna, current distribution tends to travel at the edges of the tapered element. Because of this, low frequency bands are not achievable with the standard Vivaldi tapered slot unless a very large element is provided. However, because large antennas are not desirable with modern electronics, a large conventional Vivaldi antenna is not a suitable solution for applications where ultra-wideband and low frequency characteristics are desired.
There is a need for ultra-wideband antennas capable of low frequency resonances for use in modern communications devices.